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Photosynthetic acclimation to elevated CO 2 in Phaseolus vulgaris L. is altered by growth response to nitrogen supply
Author(s) -
Jifon John L.,
Wolfe David W.
Publication year - 2002
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1046/j.1365-2486.2002.00531.x
Subject(s) - phaseolus , photosynthesis , acclimatization , nitrogen , zoology , botany , horticulture , chemistry , biology , organic chemistry
Long‐term exposure of plants to elevated CO 2 often leads to downward photosynthetic acclimation. Nitrogen (N) deficiency could potentially exacerbate this response by reducing growth rate and the sink for photosynthates, but this has not always been observed. Experimentally, the interpretation of N effects on CO 2 responses can be confounded by increasing severity of tissue N deficiency over time when N supply is not adjusted as demand increases. In this study, N supply ranged from sub‐ to supra‐optimal (20–540 kgN ha –l equivalent), and relatively stable levels of tissue N concentration were obtained in all treatments by varying twice‐weekly application rates in proportion to plant growth. The effects of N on photosynthesis and growth of beans ( Phaseolus vulgaris L.) raised at ambient (35 Pa) and three elevated (70, 105, 140 Pa) CO 2 partial pressures ( p CO 2 ) were evaluated. Averaging across N treatments, leaf total non‐structural carbohydrates (TNC) were 2.5‐ to 3‐fold higher and leaf N concentrations were 31–35% lower at elevated compared to ambient p CO 2 . Light‐saturated net CO 2 assimilation rates measured at growth p CO 2 ( A satg ) were significantly higher (26–40% depending on N supply) in plants grown at elevated compared to ambient p CO 2 . When measured at a common p CO 2 of 35 Pa, the A sat of plants grown at elevated CO 2 was 15–29% less than that of plants grown at 35 Pa, indicative of downward photosynthetic acclimation. The magnitude of downward photosynthetic acclimation to elevated CO 2 was greater in plants grown at high (180 and 540 kgN ha –l ) compared to low (20 and 60 kgN ha –l ) N supply, and this was associated with a higher A sat at growth p CO 2 , higher leaf area ratio (leaf area/total biomass), and higher TNC in leaves of high‐N plants. Our results indicate that the effect of N on acclimation to CO 2 will depend on the balance between supply and demand for N during the growing period, and the effect this has on biomass allocation and source‐sink C balance at the whole‐plant level.